Symmetric battery and method of making a symmetric battery

Abstract

The application provides a symmetrical battery and a preparation method of the symmetrical battery. The symmetrical battery comprises a first pair of electrodes, a first diaphragm, a first working electrode, a second diaphragm, a second working electrode, a third diaphragm and a second pair of electrodes which are sequentially stacked. The first working electrode comprises a first main body and a first electrode layer connected with each other, the second working electrode comprises a second main body and a second electrode layer connected with each other, the first pair of electrodes comprises a third main body and a third electrode layer connected with each other, the second pair of electrodes comprises a fourth main body and a fourth electrode layer connected with each other, the first main body is provided with a first through hole corresponding to the third electrode layer, the second main body is provided with a second through hole corresponding to the fourth electrode layer, and the first diaphragm is provided with a porous structure corresponding to the area of the first through hole, the second diaphragm is provided with a porous structure corresponding to the areas of the first through hole and the second through hole, and the third diaphragm is provided with a porous structure corresponding to the area of the second through hole. The application aims to improve the technical problems that the existing symmetrical battery has a complex process when testing different states of charge and is easy to be damaged.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to a symmetrical battery and a preparation method of the symmetrical battery. BACKGROUND

[0002] The internal resistance is an important performance index of a power battery, and the liquid phase resistance is a commonly used method for measuring the internal resistance of a lithium battery. The symmetrical battery and the three-electrode are the main methods for evaluating the liquid phase resistance of the pole piece of the lithium battery. Both methods have certain limitations. The resistance obtained by the three-electrode test method contains a reference electrode, so that the final test resistance has a certain deviation from the true resistance of the pole piece.

[0003] The symmetrical battery is usually prepared by disassembling the lithium ion battery after charging and discharging to a specific SOC (State of Charge), taking out the positive pole piece (or negative pole piece), and cutting the same two pieces to prepare the symmetrical battery. When different SOCs need to be tested, the symmetrical battery needs to be disassembled and reassembled into a lithium ion battery, and then the pole piece is taken out to prepare a symmetrical battery after charging and discharging to another SOC. The disadvantage of this method is that the process is complicated, the pole piece will be exposed to air during disassembly, and the original state of the battery will be damaged during assembly. SUMMARY

[0004] Embodiments of the present application provide a symmetrical battery and a preparation method of the symmetrical battery, which can improve the technical problems of existing symmetrical batteries, such as complex process, easy damage, and different charge states.

[0005] In a first aspect, embodiments of the present application provide a symmetrical battery, comprising: a first pair of electrodes, a first separator, a first working electrode, a second separator, a second working electrode, a third separator, and a second pair of electrodes which are sequentially stacked.

[0006] The first working electrode comprises a first main body and a first electrode layer connected thereto, the first electrode layer is located between the first main body and the second separator, the second working electrode comprises a second main body and a second electrode layer connected thereto, the second electrode layer is located between the second main body and the second separator, and the polarities of the first electrode layer and the second electrode layer are the same.

[0007] The first pair of electrodes comprises a third main body and a third electrode layer connected thereto, the third electrode layer is located between the third main body and the first separator, the second pair of electrodes comprises a fourth main body and a fourth electrode layer connected thereto, the fourth electrode layer is located between the fourth main body and the third separator, and the polarities of the third electrode layer and the fourth electrode layer are opposite to that of the first electrode layer.

[0008] The first main body is provided with a first via hole corresponding to the third electrode layer, and the second main body is provided with a second via hole corresponding to the fourth electrode layer. The first diaphragm is of a porous structure corresponding to the area of the first via hole, the second diaphragm is of a porous structure corresponding to the area of the first via hole and the second via hole, and the third diaphragm is of a porous structure corresponding to the area of the second via hole.

[0009] In an embodiment, the projection plane of the third electrode layer is located in the first via hole in the positive direction projection of the first pair of electrodes towards the first working electrode.

[0010] In an embodiment, the projection plane of the fourth electrode layer is located in the second via hole in the positive direction projection of the second pair of electrodes towards the second working electrode.

[0011] In an embodiment, the first main body comprises a first conductive sheet and a first connecting tab connected to the edge of the first conductive sheet, the first electrode layer is arranged on the surface of the first conductive sheet facing the second diaphragm, and the first conductive sheet is provided with the first via hole.

[0012] The second main body comprises a second conductive sheet and a second connecting tab connected to the edge of the second conductive sheet, the second electrode layer is arranged on the surface of the second conductive sheet facing the second diaphragm, and the second conductive sheet is provided with the second via hole.

[0013] The first connecting tab and the second connecting tab are both close to the same side edge of the second diaphragm.

[0014] In an embodiment, the third main body comprises:

[0015] a third conductive sheet;

[0016] a fourth conductive sheet connected to the third conductive sheet, and one side of the fourth conductive sheet away from the third conductive sheet is coated with the third electrode layer; and

[0017] a third connecting tab connected to the third conductive sheet and located outside the fourth conductive sheet.

[0018] In an embodiment, the fourth main body comprises:

[0019] a fifth conductive sheet;

[0020] a sixth conductive sheet connected to the fifth conductive sheet, and one side of the sixth conductive sheet away from the fifth conductive sheet is coated with the fourth electrode layer; and

[0021] a fourth connecting tab connected to the fifth conductive sheet and located outside the sixth conductive sheet.

[0022] In an embodiment, thicknesses of the first electrode layer, the second electrode layer, the third electrode layer, and the fourth electrode layer are D1, D2, D3, and D4, respectively, wherein 90 μm≤D1, D2, D3, D4≤140 μm.

[0023] In an embodiment, the porosity of the porous structure is 30% to 80%.

[0024] In a second aspect, embodiments of the present application provide a method for manufacturing a symmetric battery, comprising:

[0025] S10: providing a first working electrode and a second working electrode, the first working electrode comprising a first body and a first electrode layer connected to each other, the second working electrode comprising a second body and a second electrode layer connected to each other, the first electrode layer and the second electrode layer having the same polarity, the first body having a first via hole formed therein, and the second body having a second via hole formed therein;

[0026] S20: providing a first counter electrode and a second counter electrode, the first counter electrode comprising a third body and a third electrode layer connected to each other, the second counter electrode comprising a fourth body and a fourth electrode layer connected to each other, the third electrode layer and the fourth electrode layer having opposite polarity to the first electrode layer;

[0027] S30: providing a first separator, a second separator, and a third separator, each of the first separator, the second separator, and the third separator having a porous structure in at least a partial region thereof;

[0028] S40: sequentially stacking the first counter electrode, the first separator, the first working electrode, the second separator, the second working electrode, the third separator, and the second counter electrode to form a soft-pack module, the first via hole being oppositely arranged to the third electrode layer, the second via hole being oppositely arranged to the fourth electrode layer, the porous structure of the first separator being oppositely arranged to the first via hole, the porous structure of the second separator being oppositely arranged to the first via hole and the second via hole, and the porous structure of the third separator being oppositely arranged to the second via hole;

[0029] S50: packaging the soft-pack module.

[0030] In an embodiment, the step of providing the first working electrode comprises:

[0031] providing a first conductive sheet, and connecting a first connecting tab to an edge of the first conductive sheet to form the first body;

[0032] coating an active material on a side surface of the first conductive sheet to form the first electrode layer;

[0033] The first via hole is formed on the first conductive sheet.

[0034] Advantages of embodiments of the present application:

[0035] In the embodiment of the symmetrical battery of the present application, ion transmission can be carried out between the first electrode layer of the first working electrode and the fourth electrode layer of the second counter electrode, and ion transmission can be carried out between the second electrode layer of the second working electrode and the third electrode layer of the first counter electrode. Thus, when testing, only the first working electrode and the second counter electrode are electrically connected, and the second working electrode and the first counter electrode are electrically connected, so that the first electrode layer of the first working electrode and the second electrode layer of the second working electrode can be charged and discharged to a specific state of charge, and then the first working electrode and the second working electrode are electrically connected to perform AC impedance testing. Compared with ordinary symmetrical batteries, when different states of charge need to be tested, the first working electrode and the second working electrode can be charged and discharged without disassembling the symmetrical battery, avoiding the disadvantage that contact with air during disassembly changes the state of charge, and also avoiding the problem that multiple disassembling processes are easy to damage. The process and timeliness are greatly optimized, and the technical problems of complex process and easy damage when testing different states of charge of existing symmetrical batteries are improved. BRIEF DESCRIPTION OF DRAWINGS

[0036] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0037] Figure 1 is a cross-sectional schematic diagram of the symmetrical battery provided by the first embodiment of the present application;

[0038] Figure 2 is an exploded structural schematic diagram of the symmetrical battery provided by the first embodiment of the present application;

[0039] Figure 3 is a flowchart of the preparation method of the symmetrical battery provided by the second embodiment of the present application. DETAILED DESCRIPTION

[0040] The technical solutions in the embodiments of the present application will be clearly and completely described with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, but not all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application. In addition, it should be understood that the specific implementation described herein is only used to illustrate and explain the present application, and is not used to limit the present application. In the present application, the orientation words such as 'upper' and 'lower' generally refer to the upper and lower in the actual use or working state of the device, and specifically refer to the direction of the drawing surface in the drawings; and 'inner' and 'outer' refer to the contour of the device.

[0041] Embodiment 1, with reference to Figure 1 and Figure 2 The embodiment provides a symmetrical battery 100, which comprises a first pair of electrodes 10, a first diaphragm 20, a first working electrode 30, a second diaphragm 40, a second working electrode 50, a third diaphragm 60 and a second pair of electrodes 70 which are sequentially stacked.

[0042] The first working electrode 30 comprises a first main body 31 and a first electrode layer 32 connected with each other. The first electrode layer 32 is located between the first main body 31 and the second diaphragm 40. The second working electrode 50 comprises a second main body 51 and a second electrode layer 52 connected with each other. The second electrode layer 52 is located between the second main body 51 and the second diaphragm 40. The polarities of the first electrode layer 32 and the second electrode layer 52 are the same.

[0043] The first pair of electrodes 10 comprises a third main body 11 and a third electrode layer 12 connected with each other. The third electrode layer 12 is located between the third main body 11 and the first diaphragm 20. The second pair of electrodes 70 comprises a fourth main body 71 and a fourth electrode layer 72 connected with each other. The fourth electrode layer 72 is located between the fourth main body 71 and the third diaphragm 60. The polarities of the third electrode layer 12 and the fourth electrode layer 72 are opposite to that of the first electrode layer 32.

[0044] The first main body 31 is provided with a first through hole 3111 corresponding to the third electrode layer 12. The second main body 51 is provided with a second through hole 5111 corresponding to the fourth electrode layer 72. The region of the first diaphragm 20 corresponding to the first through hole 3111, the region of the second diaphragm 40 corresponding to the first through hole 3111 and the second through hole 5111 and the region of the third diaphragm 60 corresponding to the second through hole 5111 are porous structures.

[0045] In the embodiment of the symmetrical battery 100 of the present application, ion transmission can be carried out between the first electrode layer 32 of the first working electrode 30 and the fourth electrode layer 72 of the second counter electrode 70, and ion transmission can be carried out between the second electrode layer 52 of the second working electrode 50 and the third electrode layer 12 of the first counter electrode 10. Thus, when testing, only by electrically connecting the first working electrode 30 and the second counter electrode 70, and electrically connecting the second working electrode 50 and the first counter electrode 10, the first electrode layer 32 of the first working electrode 30 and the second electrode layer 52 of the second working electrode 50 can be charged and discharged to a specific state of charge, and then the first working electrode 30 and the second working electrode 50 are electrically connected for AC impedance testing. Compared with the ordinary symmetrical battery 100, when the different states of charge need to be tested, the first working electrode 30 and the second working electrode 50 can be charged and discharged without disassembling the symmetrical battery 100, avoiding the disadvantage that the contact with air during disassembly changes the charging state, and avoiding the problem that multiple disassembly processes are easy to damage, greatly optimizing the process and timeliness, and improving the technical problems of the existing symmetrical battery 100 that the process is complex and easy to damage when testing different states of charge.

[0046] Among them, the first electrode layer 32 and the second electrode layer 52 can be both positive electrodes, such as lithium cobaltate, lithium manganate, ternary material, lithium iron phosphate and the like. And the third electrode layer 12 and the fourth electrode layer 72 are negative electrodes, such as graphite, silicon negative material and the like. Thus, after the first working electrode 30 and the second counter electrode 70 are electrically connected, ion transmission can be carried out between the first electrode layer 32 and the fourth electrode layer 72. Similarly, when the second working electrode 50 and the first counter electrode 10 are electrically connected, ion transmission can be carried out between the second electrode layer 52 and the third electrode layer 12. Of course, the first electrode layer 32 and the second electrode layer 52 can also be negative electrodes, made of, for example, graphite, silicon negative material and the like, while the third electrode layer 12 and the fourth electrode layer 72 are positive electrodes, made of, for example, lithium cobaltate, lithium manganate, ternary material, lithium iron phosphate and the like. In addition, the first main body 31 and the second main body 51 can be the same shape and size, and the first via hole 3111 on the first main body 31 and the second via hole 5111 on the second main body 51 are both circular or square holes, and are coaxially arranged at the center, so as to facilitate unified processing. And the positions of the first working electrode 30 and the second working electrode 50 can be interchanged, as long as the first electrode layer 32 and the second electrode layer 52 are arranged face to face, so as to further improve the preparation efficiency. The third main body 11 and the fourth main body 71 can be the same shape and size, so as to facilitate unified processing. And the positions of the first counter electrode 10 and the second counter electrode 70 can be interchanged.

[0047] It should be noted that the first diaphragm 20, the second diaphragm 40 and the third diaphragm 60 are used to avoid the first working electrode 30, the second working electrode 50, the first counter electrode 10 and the second counter electrode 70 from being attached. And the regions of the first diaphragm 20 corresponding to the first via hole 3111, the second diaphragm 40 corresponding to the first via hole 3111 and the second via hole 5111, and the third diaphragm 60 corresponding to the second via hole 5111 are porous structures to provide lithium ions to pass through during charging and discharging. In order to facilitate the setting, the first diaphragm 20, the second diaphragm 40 and the third diaphragm 60 can also be made of a material with a porous structure. For example, the material of the first diaphragm 20, the second diaphragm 40 and the third diaphragm 60 is a PP film layer, a PE film layer, a PET non-woven fabric layer, a PVDF coating layer (polyvinylidene difluoride) and an oxide ceramic coating layer, etc. Further, the first diaphragm 20, the second diaphragm 40 and the third diaphragm 60 can also be stacked by multiple film layers. The thickness of the first diaphragm 20, the second diaphragm 40 and the third diaphragm 60 ranges from 10μm to 16μm, for example, 10μm, 13μm, 16μm, etc., so as to ensure that the attachment distance of the counter electrode and the working electrode is not too close, and at the same time, to facilitate the ions to pass through the first diaphragm 20, the second diaphragm 40 and the third diaphragm 60 faster during charging and discharging.

[0048] Further, the porosity of the porous structure is 30% to 80%. The porosity of the porous structure can be 30%, 40%, 50%, 60%, 70% and 80%, etc., so as to facilitate the passage of lithium ions during charging and discharging. Optionally, the thickness D1 of the first electrode layer 32, the thickness D2 of the second electrode layer 52, the thickness D3 of the third electrode layer 12 and the thickness D4 of the fourth electrode layer 72. Wherein, 90μm≤D1, D2, D3, D4≤140μm. It can be understood that the first electrode layer 32, the second electrode layer 52, the third electrode layer 12 and the fourth electrode layer 72 are formed by coating, and the specific thickness of the above electrode layer can be 90μm, 100μm, 110μm, 120μm, 130μm and 140μm, etc., so as to ensure the stability of ion transmission between electrode layers.

[0049] Referring to Figure 1 and Figure 2 Optionally, along the positive direction projection of the first counter electrode 10 towards the first working electrode 30, the projection surface of the third electrode layer 12 is located within the first via hole 3111. Thus, the area of the first via hole 3111 is greater than or equal to the area of the third electrode layer 12. During the charging and discharging process, the ions on the third electrode layer 12 of the first counter electrode 10 can pass through the first via hole 3111 to the second electrode layer 52 of the second working electrode 50 more conveniently.

[0050] Optionally, the projection of the fourth electrode layer 72 in the positive direction of the second working electrode 50 along the second pair of electrodes 70 is located within the second via hole 5111. Thus the area of the second via hole 5111 is greater than or equal to the area of the fourth electrode layer 72. During the charging and discharging process, the ions on the fourth electrode layer 72 of the second pair of electrodes 70 can more easily pass through the second via hole 5111 to the first electrode layer 32 of the first working electrode 30.

[0051] Referring to Figure 1 and Figure 2 Optionally, the first body 31 includes a first conductive sheet 311 and a first connecting tab 312 connected to the edge of the first conductive sheet 311, the first electrode layer 32 is arranged on the surface of the first conductive sheet 311 facing the second diaphragm 40, and the first conductive sheet 311 is provided with a first via hole 3111. The second body 51 includes a second conductive sheet 511 and a second connecting tab 512 connected to the edge of the second conductive sheet 511, the second electrode layer 52 is arranged on the surface of the second conductive sheet 511 facing the second diaphragm 40, and the second conductive sheet 511 is provided with a second via hole 5111. The first connecting tab 312 and the second connecting tab 512 are located on the same side of the second diaphragm 40. Among them, the first conductive sheet 311 and the second conductive sheet 511 can be made of the same metal material, such as aluminum or copper, and have the same size to facilitate unified processing. The first connecting tab 312 and the second connecting tab 512 can be fixed to the edge of the first conductive sheet 311 and the edge of the second conductive sheet 511 respectively by welding, so as to avoid the first electrode layer 32 and the second electrode layer 52. Thus, the stability of the first connecting tab 312 and the second connecting tab 512 after being arranged is ensured, and the first connecting tab 312 and the second connecting tab 512 can be used for clamping connection during subsequent electrical connection. The first connecting tab 312 and the second connecting tab 512 are both close to the same side of the second diaphragm 40, so as to further facilitate the subsequent electrical connection operation.

[0052] Optionally, the third body 11 comprises a third conductive sheet 111, a fourth conductive sheet 112 and a third connecting tab 113. The fourth conductive sheet 112 is connected to the third conductive sheet 111, and the fourth conductive sheet 112 is coated with the third electrode layer 12 on the side away from the third conductive sheet 111. The third connecting tab 113 is connected to the third conductive sheet 111 and located outside the fourth conductive sheet 112. The third conductive sheet 111 and the fourth conductive sheet 112 are made of the same metal material, such as aluminum or copper. The third conductive sheet 111 can have the same size and shape as the first conductive sheet 311 and the second conductive sheet 511 for unified processing. The fourth conductive sheet 112 is smaller than the third conductive sheet 111, which not only facilitates the preparation of the third electrode layer 12, but also ensures the stability of the fourth conductive sheet 112 after being arranged. The fourth conductive sheet 112 is coated with a layer of active material to form the third electrode layer 12, and then the fourth conductive sheet 112 can be fixed to the third conductive sheet 111 by adhesive tape, which not only facilitates operation, but also ensures the stability of the connection between the third conductive sheet 111 and the fourth conductive sheet 112. Further, the fourth conductive sheet 112 can be located in the middle of the third conductive sheet 111, which further improves the stability of the fourth conductive sheet 112 after being arranged. The fourth conductive sheet 112 is located in the middle of the third conductive sheet 111, so that there is no active material around the third conductive sheet 111, which facilitates the welding of the third connecting tab 113 at any position around the edge of the third conductive sheet 111 to adapt to different test scenarios.

[0053] Referring to Figure 1 and Figure 2Optionally, the fourth main body 71 comprises a fifth conductive sheet 711, a sixth conductive sheet 712 connected to the fifth conductive sheet 711, and a fourth connecting tab 713 connected to the fifth conductive sheet 711 and located outside the sixth conductive sheet 712. The fifth conductive sheet 711 and the sixth conductive sheet 712 are made of the same metal material, such as aluminum or copper. The fifth conductive sheet 711 can have the same shape and size as the first conductive sheet 311 and the second conductive sheet 511 for unified processing. The sixth conductive sheet 712 is smaller than the fifth conductive sheet 711, which not only facilitates the preparation of the fourth electrode layer 72, but also ensures the stability of the sixth conductive sheet 712. The sixth conductive sheet 712 is coated with a layer of active material to form the fourth electrode layer 72, and then the sixth conductive sheet 712 is fixed to the fifth conductive sheet 711 by adhesive tape, which facilitates operation and ensures the stability of the connection between the fifth conductive sheet 711 and the sixth conductive sheet 712. Further, the sixth conductive sheet 712 can be located in the middle of the fifth conductive sheet 711, which further improves the stability of the sixth conductive sheet 712. The fifth conductive sheet 711 has no active material around it, so the fourth connecting tab 713 can be welded at any position around the edge of the fifth conductive sheet 711 to adapt to different test scenarios. It should be noted that the third connecting tab 113 and the fourth connecting tab 713 can be located on the same side of the second diaphragm 40, and the third connecting tab 113 and the first connecting tab 312 are located on opposite sides of the second diaphragm 40, which makes subsequent connection more convenient.

[0054] Referring to Figure 3 , in embodiment 2, a method for manufacturing a symmetric battery 100 is provided, and the specific manufacturing steps are as follows:

[0055] In combination Figure 1 and Figure 2 , S10: providing a first working electrode 30 and a second working electrode 50, the first working electrode 30 comprising a first main body 31 and a first electrode layer 32 connected thereto, the second working electrode 50 comprising a second main body 51 and a second electrode layer 52 connected thereto, the first electrode layer 32 and the second electrode layer 52 having the same polarity, the first main body 31 having a first via hole 3111 formed therein, and the second main body 51 having a second via hole 5111 formed therein;

[0056] S20: providing a first electrode pair 10 and a second electrode pair 70, the first electrode pair 10 comprising a third main body 11 and a third electrode layer 12 connected with each other, the second electrode pair 70 comprising a fourth main body 71 and a fourth electrode layer 72 connected with each other, the third electrode layer 12 and the fourth electrode layer 72 being opposite in polarity to the first electrode layer 32;

[0057] S30: providing a first separator 20, a second separator 40 and a third separator 60, each of the first separator 20, the second separator 40 and the third separator 60 being at least partially porous;

[0058] S40: sequentially stacking the first electrode pair 10, the first separator 20, the first working electrode 30, the second separator 40, the second working electrode 50, the third separator 60 and the second electrode pair 70 to form a soft pack module, the first via hole 3111 being oppositely arranged with the third electrode layer 12, the second via hole 5111 being oppositely arranged with the fourth electrode layer 72, and the porous structure of the first separator 20 being oppositely arranged with the first via hole 3111, the porous structure of the second separator 40 being oppositely arranged with the first via hole 3111 and the second via hole 5111, and the porous structure of the third separator 60 being oppositely arranged with the second via hole 5111;

[0059] S50: packaging the soft pack module.

[0060] It can be understood that in the symmetrical battery 100 manufactured by the manufacturing method of the symmetrical battery 100 provided in Embodiment 2, ion transmission can be performed between the first electrode layer 32 of the first working electrode 30 and the fourth electrode layer 72 of the second electrode pair 70, and ion transmission can be performed between the second electrode layer 52 of the second working electrode 50 and the third electrode layer 12 of the first electrode pair 10. Thus, when testing, only the first working electrode 30 and the second electrode pair 70 need to be electrically connected, and the second working electrode 50 and the first electrode pair 10 need to be electrically connected, so that the first electrode layer 32 of the first working electrode 30 and the second electrode layer 52 of the second working electrode 50 can be charged and discharged to a specific state of charge, and then the first working electrode 30 and the second working electrode 50 are electrically connected to perform AC impedance testing. Compared with ordinary symmetrical batteries 100, when the symmetrical battery 100 needs to be tested at different states of charge, the first working electrode 30 and the second working electrode 50 can be charged and discharged without disassembling the symmetrical battery 100, avoiding the disadvantage that contact with air during disassembly changes the charging state, and avoiding the problem that multiple disassembling processes are easy to damage. The process and timeliness are greatly optimized, and the technical problems of complex process and easy damage when testing different states of charge of the existing symmetrical battery 100 are improved. The manufacturing method of the symmetrical battery 100 will be described in detail below:

[0061] in combination with Figure 1 and Figure 2 S10: providing a first working electrode 30 and a second working electrode 50, the first working electrode 30 comprising a first main body 31 and a first electrode layer 32 connected with each other, the second working electrode 50 comprising a second main body 51 and a second electrode layer 52 connected with each other, the first electrode layer 32 and the second electrode layer 52 having the same polarity, the first main body 31 being provided with a first via hole 3111, and the second main body 51 being provided with a second via hole 5111. Wherein, the first working electrode 30 and the second working electrode 50 are prepared in the same way, so as to improve the preparation efficiency.

[0062] Optionally, the step of providing the first working electrode 30 comprises:

[0063] providing a first conductive sheet 311, and connecting a first connecting tab 312 to the edge of the first conductive sheet 311 to form the first main body 31; wherein the first conductive sheet 311 is made of metal, such as aluminum or copper, and the first connecting tab 312 can be fixed to the edge of the first conductive sheet 311 by welding, so as to ensure the stability of the first connecting tab 312 after being arranged.

[0064] coating an active material on one side surface of the first conductive sheet 311 to form the first electrode layer 32; wherein, when the first electrode layer 32 is used as a positive electrode, the active material can be lithium cobalt oxide, lithium manganate, ternary material, lithium iron phosphate, etc.

[0065] forming the first via hole 3111 on the first conductive sheet 311. Wherein, the first via hole 3111 can be formed by cutting a part of the middle of the first conductive sheet 311, and the first via hole 3111 is a circular hole or a square hole.

[0066] Similarly, the second main body 51 of the second working electrode 50 comprises a second conductive sheet 511 and a second connecting tab 512 connected to the edge of the second conductive sheet 511.

[0067] S20: providing a first counter electrode 10 and a second counter electrode 70, the first counter electrode 10 comprising a third main body 11 and a third electrode layer 12 connected with each other, the second counter electrode 70 comprising a fourth main body 71 and a fourth electrode layer 72 connected with each other, the third electrode layer 12 and the fourth electrode layer 72 having a polarity opposite to that of the first electrode layer 32. Wherein, the first counter electrode 10 and the second counter electrode 70 are prepared in the same way, so as to improve the preparation efficiency.

[0068] The preparation steps of the first counter electrode 10 comprise:

[0069] The third conductive sheet 111 and the fourth conductive sheet 112 are provided, and the fourth conductive sheet 112 is adhered and fixed to the third conductive sheet 111 to form the third main body 11; the third conductive sheet 111 and the fourth conductive sheet 112 are also made of the same metal material, such as aluminum or copper, and the size of the fourth conductive sheet 112 is smaller than that of the third conductive sheet 111, so that the preparation of the third electrode layer 12 is facilitated, and the fourth conductive sheet 112 is located on the inner side of the third conductive sheet 111 to ensure the stability of the fourth conductive sheet 112 after being arranged.

[0070] An active material is coated on the surface of the fourth conductive sheet 112 away from the third conductive sheet 111 to form the third electrode layer 12; wherein when the third electrode layer 12 is a negative electrode, the active material is graphite or silicon.

[0071] The third connecting tab 113 is welded on the edge of the third conductive sheet 111; wherein the fourth conductive sheet 112 is located in the middle of the third conductive sheet 111, so that there is no active material around the third conductive sheet 111, so that the third connecting tab 113 can be welded at any position around the edge of the third conductive sheet 111 to adapt to different test scenarios.

[0072] Therefore, the fourth main body 71 includes the fifth conductive sheet 711, the sixth conductive sheet 712 connected to the fifth conductive sheet 711, the fourth electrode layer 72 coated on the side of the sixth conductive sheet 712 away from the fifth conductive sheet 711, and the fourth connecting tab 713 connected to the fifth conductive sheet 711.

[0073] S30: providing a first diaphragm 20, a second diaphragm 40 and a third diaphragm 60, wherein at least part of the first diaphragm 20, the second diaphragm 40 and the third diaphragm 60 is a porous structure. Wherein the first diaphragm 20, the second diaphragm 40 and the third diaphragm 60 are completely made of a material with a porous structure. For example, the material of the first diaphragm 20, the second diaphragm 40 and the third diaphragm 60 is a PP film layer, a PE film layer, a PET non-woven fabric layer, a PVDF coating layer (Poly Vinyli Denedi Fluoride, polyvinyl fluoride) and an oxide ceramic coating layer. Further, the first diaphragm 20, the second diaphragm 40 and the third diaphragm 60 can also be stacked by multiple film layers. The thickness of the first diaphragm 20, the second diaphragm 40 and the third diaphragm 60 ranges from 10 μm to 16 μm, for example, 10 μm, 13 μm, 16 μm, etc.

[0074] S40: sequentially stack the first counter electrode 10, the first diaphragm 20, the first working electrode 30, the second diaphragm 40, the second working electrode 50, the third diaphragm 60, and the second counter electrode 70 to form a soft package module, the first via hole 3111 is arranged opposite to the third electrode layer 12, the second via hole 5111 is arranged opposite to the fourth electrode layer 72, and the porous structure of the first diaphragm 20 is arranged opposite to the first via hole 3111, the porous structure of the second diaphragm 40 is arranged opposite to the first via hole 3111 and the second via hole 5111, and the porous structure of the third diaphragm 60 is arranged opposite to the second via hole 5111.

[0075] The first counter electrode 10, the first diaphragm 20, the first working electrode 30, the second diaphragm 40, the second working electrode 50, the third diaphragm 60, and the second counter electrode 70 are sequentially arranged in the aluminum-plastic film in a set order to form a soft package module, the first electrode layer 32 and the second electrode layer 52 are aligned face to face, the first via hole 3111 is arranged opposite to the third electrode layer 12, the second via hole 5111 is arranged opposite to the fourth electrode layer 72, the porous structure of the first diaphragm 20 is arranged opposite to the first via hole 3111, the porous structure of the second diaphragm 40 is arranged opposite to the first via hole 3111 and the second via hole 5111, and the porous structure of the third diaphragm 60 is arranged opposite to the second via hole 5111. At the same time, the first connecting tab 312, the second connecting tab 512, the third connecting tab 113, and the fourth connecting tab 713 all extend out of the aluminum-plastic film.

[0076] S50: package the soft package module. Before packaging, 3ml of electrolyte is injected into the aluminum-plastic film using a syringe, and then sealed. After standing for 48 hours, a symmetrical battery 100 is formed. Then, the first working electrode 30 can be charged and discharged to adjust its state of charge by electrically connecting the first connecting tab 312 and the fourth connecting tab 713, and the second working electrode 50 can be charged and discharged to adjust its state of charge by electrically connecting the second connecting tab 512 and the third connecting tab 113. Then, the first connecting tab 312 and the second connecting tab 512 can be electrically connected to perform an AC impedance test, and the measurement range is 1MHz to 1Hz, and the voltage is 5mV.

[0077] The above describes the embodiments of the present application in detail, and the specific examples are applied to explain the principles and implementation modes of the present application; the above description of the embodiments is only used to help understand the method of the present application and its core idea; meanwhile, for those skilled in the art, the specific implementation mode and application range can be changed according to the idea of the present application, and the above description of the present application should not be understood as a limitation.

Claims

1. A symmetric battery, characterized by, The application relates to a battery electrode, which comprises a first pair of electrodes, a first diaphragm, a first working electrode, a second diaphragm, a second working electrode, a third diaphragm and a second pair of electrodes arranged in sequence. The first working electrode comprises a first main body and a first electrode layer connected to each other, the first electrode layer is located between the first main body and the second diaphragm, the second working electrode comprises a second main body and a second electrode layer connected to each other, the second electrode layer is located between the second main body and the second diaphragm, the first electrode layer and the second electrode layer have the same polarity. The first pair of electrodes comprises a third main body and a third electrode layer connected to each other, the third electrode layer is located between the third main body and the first diaphragm, the second pair of electrodes comprises a fourth main body and a fourth electrode layer connected to each other, the fourth electrode layer is located between the fourth main body and the third diaphragm, the third electrode layer and the fourth electrode layer have the opposite polarity of the first electrode layer. The first main body is provided with a first through hole corresponding to the third electrode layer, the second main body is provided with a second through hole corresponding to the fourth electrode layer, and the first diaphragm, the second diaphragm and the third diaphragm are of a porous structure corresponding to the regions of the first through hole, the first through hole and the second through hole and the region of the second through hole. Along the positive direction projection of the first pair of electrodes towards the first working electrode, the projection surface of the third electrode layer is located in the first through hole.

2. The symmetric battery of claim 1, wherein, Along the positive direction projection of the second pair of electrodes towards the second working electrode, the projection surface of the fourth electrode layer is located in the second through hole.

3. The symmetric battery of claim 1, wherein, The first main body comprises a first conductive sheet and a first connecting tab connected to the edge of the first conductive sheet, the first electrode layer is arranged on the surface of the first conductive sheet facing the second diaphragm, and the first conductive sheet is provided with the first through hole.

4. The symmetric battery of claim 1, wherein, The second main body comprises a second conductive sheet and a second connecting tab connected to the edge of the second conductive sheet, the second electrode layer is arranged on the surface of the second conductive sheet facing the second diaphragm, and the second conductive sheet is provided with the second through hole. The first connecting tab and the second connecting tab are close to the same side of the second diaphragm. The third main body comprises:

5. The symmetric battery of claim 1, wherein, a third conductive sheet; a fourth conductive sheet connected to the third conductive sheet, and one side of the fourth conductive sheet away from the third conductive sheet is coated with the third electrode layer; and a third connecting tab connected to the third conductive sheet and located outside the fourth conductive sheet. The fourth main body comprises:

6. The symmetric battery of claim 1, wherein, a fifth conductive sheet; a sixth conductive sheet connected to the fifth conductive sheet, and one side of the sixth conductive sheet away from the fifth conductive sheet is coated with the fourth electrode layer; and a fourth connecting tab connected to the fifth conductive sheet and located outside the sixth conductive sheet. The thickness of the first electrode layer is D1, the thickness of the second electrode layer is D2, the thickness of the third electrode layer is D3, and the thickness of the fourth electrode layer is D4; wherein 90 mu m<=D1, D2, D3, D4<=140 mu m.

7. The symmetric battery according to any one of claims 1 to 6, characterized in that, ​ 8. The symmetric battery according to any one of claims 1 to 6, characterized in that The porosity of the porous structure is 30% to 80%.

9. A method of preparing a symmetric battery, characterized by, Comprise: S10: providing a first working electrode and a second working electrode, the first working electrode comprising a first body and a first electrode layer connected thereto, the second working electrode comprising a second body and a second electrode layer connected thereto, the first electrode layer and the second electrode layer having the same polarity, the first body being provided with a first via hole, and the second body being provided with a second via hole; S20: providing a first counter electrode and a second counter electrode, the first counter electrode comprising a third body and a third electrode layer connected thereto, the second counter electrode comprising a fourth body and a fourth electrode layer connected thereto, the third electrode layer and the fourth electrode layer having a polarity opposite to that of the first electrode layer; S30: providing a first diaphragm, a second diaphragm, and a third diaphragm, each of the first diaphragm, the second diaphragm, and the third diaphragm being at least partially porous; S40: sequentially stacking the first counter electrode, the first diaphragm, the first working electrode, the second diaphragm, the second working electrode, the third diaphragm, and the second counter electrode to form a soft-pack module, and the first electrode layer being located between the first body and the second diaphragm, the second electrode layer being located between the second body and the second diaphragm, the third electrode layer being located between the third body and the first diaphragm, the fourth electrode layer being located between the fourth body and the third diaphragm, the first via hole being arranged opposite to the third electrode layer, the second via hole being arranged opposite to the fourth electrode layer, and the porous structure of the first diaphragm being arranged opposite to the first via hole, the porous structure of the second diaphragm being arranged opposite to the first via hole and the second via hole, and the porous structure of the third diaphragm being arranged opposite to the second via hole; S50: packaging the soft-pack module.

10. The method of claim 9, wherein the symmetric battery is prepared by the steps of: The step of providing a first working electrode comprises: providing a first conductive sheet, and connecting a first connecting tab to an edge of the first conductive sheet to form the first body; coating an active material on one side surface of the first conductive sheet to form the first electrode layer; opening the first via hole on the first conductive sheet.

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